1. Field of the Invention
The present invention relates to a speech recognition apparatus and method for performing a speech recognition process by two-pass method.
2. Description of the Related Art
In a common speech recognition process, speech input into an apparatus is recognized by use of an acoustic model. JP-A 2004-117624 (KOKAI) discloses a method of recognizing speech by selecting an acoustic model that is suitable for the input speech from among different acoustic models. Examples of conventional speech recognition processes include a two-pass method, where recognition is carried out by use of an acoustic model that is independent of any speaker and environment in the first pass, and then by use of a specific acoustic model that is dependent on the speaker or the environment of the speech in the second pass, thereby obtaining a recognition result.
Moreover, JP 3176210 suggests a technique of applying the method described in JP-A 2004-117624 (KOKAI) to the aforementioned two-pass method. In other words, an acoustic model suitable for the input speech is selected from among multiple models while the recognition is being carried out in the first pass, and then the second-pass recognition is carried out by use of the selected model so as to attain the recognition result. This method, however, has a problem of requiring a large amount of memory resources and increasing the calculation when selecting an acoustic model for the use of the second pass.